Scarlett Johansson has stepped out on the red carpet for the first time since it was reported she is pregnant with her first child.

The Her actress, who is engaged to French journalist Romain Dauriac, wore a black and white lace tasselled dress to the world premiere of Captain America: The Winter Soldier in Los Angeles.

Scarlett resumes her role of the Black Widow for the Marvel sequel and is due to reprise it again for the Avengers follow-up.

The star is around five months pregnant according to E! and TMZ, but she recently told the Huffington Post everything is on schedule to begin shooting the hotly anticipated return of the Avengers.

"We're full steam ahead. We start shooting in three weeks and I'm stunt training and we're good to go."

Scarlett has not confirmed her pregnancy but she laughed when asked whether she's up for such a physically-demanding part at this point in her life.

"I think it's something that is hard to talk about, exactly. You know, trying to skirt around your question exactly and, you know, doing a poor job of it."

Chris Evans, who stars as the title character in Captain America was far more open about his body at the world premiere of his movie.

Asked how he gets into shape to slip into the tight costume, he said: "I wish I had a clever answer, it's just picking up heavy stuff and putting it down. It's very basic; it's a lot more simple than you think."

He added that he never loses the thrill of suiting up: "It's exciting and rewarding. The best part is knowing they will make good movies. It's not easy to make good movies, if it was there would be more of them but Marvel knows what they are doing so it's always exciting to suit back up when you know the end result will be something you will be proud of."